i am create button using below tool may useful to you :)
see this solution
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<!-- This is the line -->
<item android:top="-2dp" android:left="-2dp" android:bottom="-2dp">
<shape>
<solid android:color="@android:color/transparent" />
<stroke android:width="2dp" android:color="#21610B" />
</shape>
</item>
</layer-list>